Gum arabic is a natural polymer having an excellent emulsification ability and a low viscosity even in the form of a high concentration solution, and, because of such characteristics, has been widely used as an emulsifier in the foods and pharmaceutical fields. However, it is also known that gum arabic, when used as is, does not exhibit satisfactory emulsifying properties.
Therefore, methods for enhancing the emulsification ability of gum arabic have been studied and proposed. For example, a method wherein metal ions are removed from gum arabic to obtain arabic acid and the thus-obtained arabic acid is then thermally modified to improve (modify) its emulsification ability (Patent Document 1), and a method wherein a gum arabic having a loss-on-drying weight of not more than 50 mass % is modified by heating at 60-140° C. for not less than 30 minutes to thereby enhance (modify) its emulsification ability (Patent document 2) have been disclosed.
However, these methods have problems such as coloration of gum arabic, generation of insoluble matter, and/or unpleasant odor during the heating process.
A method of modifying gum arabic, which comprises a step of controlling the moisture content of gum arabic to 3-30 mass % and a step of heating the gum arabic at not less than 30° C., has been disclosed (for example, in Patent document 3); however, such a method does not completely prevent coloration of the gum arabic.
[Patent document 1] Japanese Unexamined Patent Publication No. 1990-49001
[Patent document 2] Japanese Unexamined Patent Publication No. 2000-166489
[Patent document 3] Japanese Unexamined Patent Publication No. 2003-321502